The invention relates to loudspeakers and in particular to a loudspeaker horn having selectable directivity in different planes and a common point at which the wavefront appears to originate in each plane.
Loudspeaker horns are well known and are used to both increase speaker output by appropriate loading of the driver and for directivity control. Appropriate loading can improve power handling and efficiency of modern compression drivers. However, directivity problems remain. To alleviate such problems, some known horn designs employ essentially separate but joined sections. In such arrangements, the first section has a cross section area that expands exponentially and the second area has constant expansion like a cone. Such combined horns have good loading and directivity over a wide range of frequencies. The design, however, is complicated.
Another arrangement for controlling directivity employs the so called Manta-Ray design which provides good loading and directivity, but exhibits severe astigmatism in the curvature of the wavefront produced by the horn. Briefly stated, the radius of curvature of a wavefront is different in the horizontal and vertical planes. The wavefront appears offset and does not seem to originate from the same point. Astigmatism can adversely affect the sound when more than one horn is employed in an array. In addition to astigmatism, such horns tend to distort the signal at high sound pressure levels and can produce reflections and diffraction which complicates the predictability of the horn operation.